
For all \(f \in D(\Delta )\) ,
\(\Delta f(x)=\operatorname{tr}(\mathrm {Hess}_f)(x)\) 
holds for \(\mathfrak {m}\) -a.e. \(x \in X\) , where the Hessian, \(\mathrm {Hess}_f\) , of \(f\)  is defined in [1]} as a \((0, 2)\) -type \(L^2\)  tensor.

(REF ) holds for some \(b, k \in (0, \infty )\) .


